JP6925396B2 - General synthetic strategies for making multimetal nanostructures - Google Patents

Description

The present disclosure relates to methods of producing hollow multimetal nanostructures.

Multimetal hollow nanostructures are promising new candidates in biomedicine, fuel cells, and gas sensors due to their porous structure and the potential for synergistic effects between two or more metals. However, known methods for synthesizing such nanostructures generally include personalized synthetic methods. Several general-purpose methods are known, but such methods are generally limited to precious metals such as silver or palladium, all of which are expensive compared to other metals such as copper. Therefore, general-purpose synthetic strategies for preparing multi-metal nanostructures are needed in the art.

The present disclosure generally relates to methods for preparing hollow multimetal two-dimensional nanostructures. The method involves preparing a first metal nanostructure and substituting a portion of the first metal atom contained in the first metal nanostructure with a corresponding number of second metal ions. It may include promoting the diffusion of the first metal atom to provide hollow nanostructures. According to some embodiments, the method may include a one-step synthetic strategy. The present disclosure also relates to hollow multimetal two-dimensional nanostructures provided by the method.

FIG. 1 shows a schematic view of an example of a method according to the aspects of the present disclosure.

FIG. 2 shows a scanning electron microscope (SEM) image of hollow Au-Cu two-dimensional nanostructures prepared according to Example II (a).

FIG. 3 shows a transmission electron microscope (TEM) image of hollow Au-Cu two-dimensional nanostructures prepared according to Example II (a).

FIG. 4 shows a high resolution TEM (HRTEM) image of hollow Au-Cu two-dimensional nanostructures prepared according to Example II (a).

FIG. 5 shows a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of hollow Au-Cu two-dimensional nanostructures prepared according to Example II (a).

FIG. 6 shows energy dispersive X-ray (EDX) mapping images of Cu elements in hollow Au-Cu two-dimensional nanostructures prepared according to Example II (a).

FIG. 7 shows an energy dispersive X-ray (EDX) mapping image of the Au element of the hollow Au-Cu two-dimensional nanostructure prepared according to Example II (a).

FIG. 8 shows the Cu—Au alloying evolution process of Example II (a) over time.

FIG. 9A shows an X-ray photoelectron spectroscopic analysis (XPS) spectrum of the Au element of the hollow Au-Cu two-dimensional nanostructure prepared according to Example II (a).

FIG. 9B shows an X-ray photoelectron spectroscopic analysis (XPS) spectrum of Cu elements in a hollow Au-Cu two-dimensional nanostructure prepared according to Example II (a).

FIG. 10 shows a scattering spectrum of hollow Au—Cu two-dimensional nanostructures prepared according to Example II (a).

FIG. 11A shows SEM and TEM images of Cu-Pd hollow nanostructures prepared according to Example II (b).

FIG. 11B shows SEM and TEM images of Cu-Pt hollow nanostructures prepared according to Example II (c).

FIG. 11C shows SEM and TEM images of Cu-Au hollow nanostructures prepared according to Example II (d).

The present disclosure generally relates to methods of preparing hollow multimetal nanostructures. The method involves preparing a first metal nanostructure and substituting a portion of the first metal atom contained in the first metal nanostructure with a corresponding number of second metal ions. It may include promoting the diffusion of the first metal atom to provide hollow nanostructures. According to some embodiments, the method may include a one-step synthetic strategy. The present disclosure also relates to hollow multimetal nanostructures provided by the method. If desired, the nanostructure may be two-dimensional.

As used herein, the term "nanostructure" refers to a structure having at least one dimension of nanosize, i.e. at least one dimension of about 0.1 to 100 nm. It should be understood that "nanostructures" include, but are not limited to, nanosheets, nanotubes, nanoparticles (eg, polyhedron nanoparticles), nanopsheres, nanowires, nanocubes, and combinations thereof. Nanosheets can include sheets with nano-sized thickness. Nanotubes may include tubes with nano-sized diameters. Nanoparticles can include particles whose spatial dimensions are nano-sized. According to some embodiments, the first metal nanostructure and the hollow multimetal two-dimensional nanostructure may be the same or different.

According to some aspects, the method may include providing first metal nanostructures, such as first metal nanosheets. It should be understood that the first metal nanostructures may be provided by any means known in the art that are compatible with the present disclosure.

For example, according to some embodiments, the first metal nanostructures may include copper nanosheets. According to some embodiments, copper nanosheets can be provided using a copper complex solution. According to some embodiments, the copper complex solution may contain one or more copper complexes. As used herein, the term "copper complex" refers to a complex of copper with one or more complexing agents. Useful complexing agents according to the present disclosure include, but are limited to, tetradecylamine (TDA), dodecylamine (DDA), hexadecylamine (HAD), octadecylamine (ODA), and oleylamine (OLA). Not done. According to some embodiments, the copper complex is allowed at an acceptable temperature by combining one or more copper atoms and / or salts thereof in solution with one or more complexing agents in an inert atmosphere. It can be provided by stirring for a length of time. For example, a copper complex can be provided by combining a copper salt with one or more complexing agents in solution under an inert gas stream. Examples of the inert gas include, but are not limited to, nitrogen gas, argon gas, and combinations thereof. The combined solution can then be heated to a temperature of about 100-300 ° C. for about 1 minute to about 1 hour to provide a copper complex solution containing the copper complex.

According to some embodiments, the copper nanosheets can be provided by heating the copper complex solution. For example, copper nanosheets can be provided by combining a copper complex solution with one or more ligands in a hot, inert atmosphere for an acceptable length of time. For example, copper nanosheets can be provided by combining a copper complex solution with a ligand at a high temperature of about 100-500 ° C., preferably about 200-400 ° C., preferably about 300 ° C. in an inert atmosphere. The combined solution may be held at high temperature for about 1 minute to 2 hours, optionally about 30 to 90 minutes, optionally about 1 hour at high temperature to provide a copper nanosheet solution containing copper nanosheets. Examples of ligands include, but are not limited to, oleylamine, trioctylphosphine, tetradecylamine, dodecylamine, octadecylamine, hexadecylamine, trioctylphosphine oxide, oleic acid, and combinations thereof.

It should be understood that the first metal atom contained in the first metal nanostructure (eg, the copper atom contained in the copper nanosheet) has a first oxidation potential. As used herein, the term "oxidation potential" refers to the change in energy required to remove an electron from a substance. It should be understood that copper can have an oxidation potential of, for example, about 0.34 V. According to some embodiments, the first metal may be a metal having a first oxidation potential of about 1.0 V or less, and optionally about 0.5 V or less. According to some embodiments, the first metal can be selected from the group consisting of copper (Cu), nickel (Ni), cobalt (Co), iron (Fe), and combinations thereof.

According to some embodiments, the method may include substituting a portion of the first metal atom contained in the first metal nanostructure with a corresponding number of second metal ions. According to some embodiments, the second metal may include a metal having a second oxidation potential higher than the first oxidation potential. Examples of metals useful in accordance with the present disclosure include, but are not limited to, gold (Au), platinum (Pt), palladium (Pd), and combinations thereof. According to some embodiments, the second oxidation potential is about 1.40V (Au ³⁺ / Au), about 1.20V (Pt ²⁺ / Pt), and / or about 0.92V (Pd ²⁺ / Pd). May be. According to some embodiments, the second oxidation potential is at least about 0.6V, optionally about 0.7V, optionally about 0.8V, optionally about 0.9V, more than the first oxidation potential. May be about 1.0 V higher. According to some embodiments, the first metal is different from the second metal.

According to some embodiments, substituting a portion of the first metal atom contained in the first metal nanostructure with a corresponding number of second metal ions replaces the first metal nanostructure solution with a metal. May include combining with precursor solution. As used herein, the term "first metal nanostructured solution" refers to a solution containing the first metal nanostructures described herein. As used herein, the term "metal precursor solution" refers to a solution containing a metal-containing compound and / or a hydrate thereof. Examples of the metal compound, chloroauric acid (HAuCl _4), palladium (II) acetylacetonate (Pd _{(acac) 2),} chloroplatinic acid _(H 2 PtCl _6), combinations thereof, and hydrates thereof However, it is not limited to these. According to some embodiments, the first metal nanostructure solution can be combined with the metal precursor solution at a temperature suitable for the second metal ion to replace the corresponding number of first metal ions. For example, at a high temperature of about 10 to 200 ° C., preferably about 50 to 180 ° C., preferably about 80 to 180 ° C., preferably about 80 to 150 ° C., the first metal nanostructure solution is combined with the metal precursor solution. good.

According to some embodiments, a second of the first metal atoms of about 5: 1 to about 1: 5, optionally about 4: 1 to 1: 4, and optionally about 3: 1 to about 1: 3. The concentration and / or amount of the first metal nanostructured solution and / or metal precursor solution may be selected to provide a combined solution having at least an initial molar ratio to metal ions.

According to some embodiments, the molar ratio of the first metal atom to the second metal ion may be selected to provide the selected composition and phase of the resulting hollow multimetal two-dimensional nanostructure. Specifically, according to some embodiments, the reaction rate of galvanic substitutions can increase with increasing concentration of metal precursors. Therefore, the kinetics of galvanic substitution can be selected by choosing a particular molar ratio of the first metal atom to the second metal ion in the combined solution.

The combined first metal nanostructure and metal precursor solution is such that some of the first metal atoms contained in the first metal nanostructure are replaced by the corresponding number of second metal ions. It can be kept at high temperature for a synthesis time of about 1 minute to 3 hours, optionally about 20 minutes to 2 hours, and optionally about 1 hour. According to some embodiments, the synthesis time may be selected to provide the selected composition and phase of the resulting hollow multimetal two-dimensional nanostructure. For example, longer synthesis times (eg, 20 minutes) can result in hollow multimetal two-dimensional nanostructures with a molar ratio of the first metal atom to the second metal atom of about 1: 1, while synthesis. Shorter times (eg, less than 5 minutes) can result in hollow multimetal two-dimensional nanostructures with a molar ratio of the first metal atom to the second metal atom of about 3: 1. Since the concentration of the first metal atom contained in the nanostructure can decrease as the reaction time increases, extending the reaction time to 40 minutes results in a molar ratio of the first metal to the second metal atom of 1: 3. Can be reduced to. The final molar ratio of the first metal to the second metal atom can reach 1: 8 with a reaction time of 60 minutes.

According to some embodiments, the portion of the first metal ion to be substituted may include a first metal ion located on or near the surface of the first metal nanostructure. Although not bound by any particular theory, since the first oxidation potential is smaller than the second oxidation potential, galvanic substitution causes the first metal atom on or near the surface of the nanostructure to become the second metal. Can be replaced by ions.

According to some embodiments, the method may include promoting the diffusion of a first metal atom to provide hollow multimetal two-dimensional nanostructures. Without being bound by any particular theory, hollow multimetal two-dimensional nanostructures are provided by the Kirkendall effect, in which the first metal atom inside the first metal nanostructure diffuses out of the nanostructure. Can be done. As used herein, the term "outside" refers to the location of the surface and / or near the surface of the nanostructure. The term "inside" refers to a location away from the surface of the nanostructure. Hollow multimetal two-dimensional nanostructures include, for example, continuous hollow centers (ie, the hollow centers extend from one side of the nanostructure to the other, forming, for example, annular or tubular nanostructures). And / or a hollow core (ie, the hollow center does not extend from one side to the other of the nanostructure, instead forming a recessed center within the nanostructure or outside the nanostructure. It should be understood that it may include (forming hollow centers that are invisible to the eye).

According to some embodiments, one or more of the other method steps described herein may promote the diffusion of the first metal atom sequentially and / or simultaneously. For example, as described herein, the first metal nanostructure solution and the metal precursor solution are combined at a high temperature suitable for the second metal ion to replace the corresponding number of first metal ions. Then, by keeping the combined solution at a high temperature, a part of the first metal atom contained in the first metal nanostructure is sequentially and / or simultaneously replaced with a corresponding number of second metal ions. , The diffusion of the first metal atom can be promoted.

According to some embodiments, the method may include a one-step synthetic strategy. As used herein, the term "one-step synthetic strategy" refers to a synthetic strategy in which at least the first reactant is converted to a reaction product in a single synthetic step. For example, as described herein, in a single synthetic step, the first metal nanostructures can be transformed into hollow multimetal two-dimensional nanostructures, specifically the first metal nanostructures. The structural solution and the metal precursor solution are combined at a high temperature and the combined solution is held at a high temperature for a specific length of time.

FIG. 1 shows a schematic view of an example of a method according to the aspects of the present disclosure. As shown in FIG. 1, the method may include providing one or more first metal nanostructures, eg, one or more copper nanosheets 11. The method may include substituting a portion of the copper atom 12 contained in the copper nanosheet with a corresponding number of second metal ions, such as Au ion 13, Pd ion 14, and / or Pt ion 15. .. As described herein, substituting a portion of the copper atoms 12 contained in a copper nanosheet with a corresponding number of second metal ions can result in one or more copper nanosheets 11 at high temperatures for a particular period of time. Can include combining a solution containing the above with a metal precursor solution. As described herein, carbon atoms can diffuse sequentially and / or simultaneously to provide the hollow multimetal two-dimensional nanostructures 16 described herein.

According to some embodiments, the method may further include one or more cleaning steps. The washing step involves centrifuging the solution containing the hollow multi-metal two-dimensional nanostructures, removing the supernatant, and combining with a solvent such as a hydrophobic solvent and / or an organic solvent. Can include centrifuging. The method may include one, two, three, or more cleaning steps.

It should be understood that the term "multimetal" as used herein refers to at least two different metals. According to some embodiments, the hollow multimetal two-dimensional nanostructure may be a hollow two-metal two-dimensional nanostructure, i.e., the only metal atom contained in the nanostructure is the first and second metal atoms. Is. However, according to some embodiments, the hollow multimetal two-dimensional nanostructures may contain three, four, five, or more different types of metal atoms.

The present disclosure also relates to hollow multimetal two-dimensional nanostructures provided by the method, including, but not limited to, Cu-Au hollow nanostructures, Cu-Pd hollow nanostructures, and Cu-Pt hollow nanostructures. According to some embodiments, the molar ratio of the first metal to the second metal atom in the hollow multi-metal two-dimensional nanostructure is from about 10: 1 to 1:10, optionally from about 5: 1 to 1: 5. It may be about 3: 1 to 1: 3 if desired, about 2: 1 to 1: 2 if desired, about 1.5: 1 to 1: 1.5 if desired, and about 1: 1 if desired.

The present disclosure also relates to methods using the hollow multimetal two-dimensional nanostructures described herein. According to some embodiments, the method may include utilizing hollow multimetal two-dimensional nanostructures in the manufacture of gas sensors and / or the use of the resulting gas sensors. According to some embodiments, the method may include using hollow multimetal two-dimensional nanostructures to catalyze the _{CO 2 reduction reaction, at least in part.}

The embodiments described herein have been described in conjunction with the exemplary embodiments outlined above, but will vary, at least to those skilled in the art, whether known or currently unexpected. Substitutes, modifications, modifications, improvements, and / or substantial equivalents can be identified. Therefore, the above exemplary embodiments are intended to be exemplary rather than limiting. Various changes may be made without departing from the spirit and scope of this disclosure. Accordingly, the present disclosure is intended to include all known or upcoming alternatives, modifications, modifications, improvements, and / or substantial equivalents.

Therefore, "Claims" is not intended to be limited to the aspects set forth herein, but is consistent with the entire scope of the "Claims" language and is singular. References to the elements of are intended to mean "one or more" rather than "unique" unless specifically stated. All structural and functional equivalents of the elements of various aspects described throughout this disclosure that are known to those of skill in the art or will be known in the future are expressly incorporated herein by reference. It is intended to be included in the scope of claims. Moreover, nothing disclosed herein is intended to be made public, whether or not such disclosure is expressly stated in the "Claims". No claim element should be construed as a means plus function unless the elements are explicitly listed using the phrase "means for".

Further, the term "example" means "playing a role as an example, instance, or illustration" herein. All aspects described herein as "Examples" should not necessarily be construed as preferred or advantageous over other aspects. Unless otherwise stated, the term "some" refers to one or more. Combinations such as "at least one of A, B, or C", "at least one of A, B, and C", and "A, B, C, or any combination thereof" are It may include any combination of A, B, and / or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, "at least one of A, B, or C", "at least one of A, B, and C", and "A, B, C, or any combination thereof". Such combinations may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, and any such combination may be of A, B, or C. One or more of them, that is, a plurality of members may be included. Nothing disclosed herein is intended to be made public, whether or not such disclosure is expressly stated in the "Claims".

As used herein, the terms "about" and "approximately" are defined as close to those understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms "about" and "approximately" are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%. ..

Example I: Preparation of copper complex solution

100mg of copper chloride (I) (99.99%), tetradecyl amine of 220mg (TDA,> 96%) , and the ODE of 2 mL, were added to a flask to remove oxygen in Ar or _{N 2} flow. After 20 minutes of foaming of Ar or N ₂ , the mixed solution was heated to 190 ° C. on a hot plate and maintained at this temperature for 30 minutes. During the heating process, TDA was melted at about 38-40 ° C. and coordinated with Cu atoms to form a blue complex solution of Cu-TDA.

Example II (a): Synthesis of Cu-Au hollow nanostructures

6.0 mL of OLA (70%) was placed in a 25 mL three-necked flask from which oxygen had been removed by blowing Ar for 10 minutes. Under Ar flow, 0.5 mL TOP (97%) and 0.5 mL TOP (90%) were injected into the flask, respectively. After running Ar for 10 minutes, the flask was rapidly heated to 300 ° C. Next, when 2 mL of the copper complex solution prepared in Example I was rapidly injected into a heated flask, the reaction solution turned red within 5 to 10 minutes, indicating that copper nanosheets were formed. Was done. The reaction was held at 300 ° C. for 60 minutes. The reaction mixture was then allowed to cool to 120 ° C., gold precursor solution _{1.0mL (0.1M, HAuCl 4 · 3H} 2 O of 39.3mg dissolved in oleylamine 1.0 mL) was injected. The reaction solution was maintained at 120 ° C. for 60 minutes. The product was separated by centrifugation at 8000 rpm for 5 minutes. The supernatant was discarded. A mixed solution of 5 mL of hexane (or another hydrophobic solvent such as toluene or chloroform) and 5 mL of ethanol was then added to the precipitate and the mixture was centrifuged at 8000 rpm for 5 minutes. The washing procedure was repeated twice to remove unreacted precursors and detergents. Prior to characterization, Cu-Au hollow nanostructures were stored in hydrophobic solvents (eg, hexane, toluene, and chloroform).

For acceptable results, the gold precursor solution injected may be 0.2 mL-3.0 mL, the injection temperature of the gold precursor solution may be 80 ° C-150 ° C, and the gold precursor solution. It was concluded that the reaction time after injecting the body solution could be 20-120 minutes.

Example II (b): Synthesis of Cu-Pd hollow nanostructures

6.0 mL of OLA (70%) was placed in a 25 mL three-necked flask from which oxygen had been removed by blowing Ar for 10 minutes. Under Ar flow, 0.5 mL TOP (97%) and 0.5 mL TOP (90%) were injected into the flask, respectively. After running Ar for 10 minutes, the flask was rapidly heated to 300 ° C. Next, when 2 mL of the copper complex solution prepared in Example I was rapidly injected into a heated flask, the reaction solution turned red within 5 to 10 minutes, indicating that copper nanosheets were formed. Was done. The reaction was held at 300 ° C. for 60 minutes. The reaction mixture was then air cooled to 150 ° C. and 1.0 mL of gold precursor solution (0.1 M, 30.4 mg Pd (acac) ₂ dissolved in 1.0 mL oleylamine) was injected. The reaction solution was maintained at 150 ° C. for 60 minutes. The product was separated by centrifugation at 8000 rpm for 5 minutes. The supernatant was discarded. A mixed solution of 5 mL of hexane (or another hydrophobic solvent such as toluene or chloroform) and 5 mL of ethanol was then added to the precipitate and the mixture was centrifuged at 8000 rpm for 5 minutes. The washing procedure was repeated twice to remove unreacted precursors and detergents. Prior to characterization, Cu-Pd hollow nanostructures were stored in hydrophobic solvents (eg, hexane, toluene, and chloroform).

For acceptable results, the palladium precursor solution injected may be 0.2 mL-3.0 mL, the injection temperature of the palladium precursor solution may be 80 ° C-180 ° C, and the gold precursor. It was concluded that the reaction time after injecting the body solution could be 20-120 minutes.

Example II (c): Synthesis of Cu-Pt hollow nanostructures

6.0 mL of OLA (70%) was placed in a 25 mL three-necked flask from which oxygen had been removed by blowing Ar for 10 minutes. Under Ar flow, 0.5 mL TOP (97%) and 0.5 mL TOP (90%) were injected into the flask, respectively. After running Ar for 10 minutes, the flask was rapidly heated to 300 ° C. Next, when 2 mL of the copper complex solution prepared in Example I was rapidly injected into a heated flask, the reaction solution turned red within 5 to 10 minutes, indicating that copper nanosheets were formed. Was done. The reaction was held at 300 ° C. for 60 minutes. The reaction mixture was then allowed to cool to 120 ° C., it was injected platinum precursor solution _{(0.1M, H 2 PtCl 6 ·} 6H 2 O of 51.7mg dissolved in oleylamine 1.0 mL) 1.0 mL. The reaction solution was maintained at 120 ° C. for 60 minutes. The product was separated by centrifugation at 8000 rpm for 5 minutes. The supernatant was discarded. A mixed solution of 5 mL of hexane (or another hydrophobic solvent such as toluene or chloroform) and 5 mL of ethanol was then added to the precipitate and the mixture was centrifuged at 8000 rpm for 5 minutes. The washing procedure was repeated twice to remove unreacted precursors and detergents. Prior to characterization, Cu-Pt hollow nanostructures were stored in hydrophobic solvents (eg, hexane, toluene, and chloroform).

For acceptable results, the platinum precursor solution injected may be 0.2 mL to 3.0 mL, the injection temperature of the platinum precursor solution may be 80 ° C. to 150 ° C., and the platinum precursor solution. It was concluded that the reaction time after injecting the body solution could be 20-120 minutes.

Example II (d): Synthesis of Cu-Au hollow nanostructures

6.0 mL of OLA (70%) was placed in a 25 mL three-necked flask from which oxygen had been removed by blowing Ar for 10 minutes. Under Ar flow, 0.2 mL TOP (97%) was injected into the flask. After running Ar for 10 minutes, the flask was rapidly heated to 300 ° C. Next, when 2 mL of the copper complex solution prepared in Example I was rapidly injected into a heated flask, the reaction solution turned red within 5 to 10 minutes, indicating that copper nanosheets were formed. Was done. The reaction was held at 300 ° C. for 20 minutes. The reaction mixture was then allowed to cool to 120 ° C., gold precursor solution _{1.0mL (0.1M, HAuCl 4 · 3H} 2 O of 50.7mg dissolved in oleylamine 1.0 mL) was injected. The reaction solution was maintained at 120 ° C. for 60 minutes. The product was separated by centrifugation at 8000 rpm for 5 minutes. The supernatant was discarded. A mixed solution of 5 mL of hexane (or another hydrophobic solvent such as toluene or chloroform) and 5 mL of ethanol was then added to the precipitate and the mixture was centrifuged at 8000 rpm for 5 minutes. The washing procedure was repeated twice to remove unreacted precursors and detergents. Prior to characterization, Cu-Au hollow nanostructures were stored in hydrophobic solvents (eg, hexane, toluene, and chloroform).

For acceptable results, the gold precursor solution injected may be 0.2 mL-3.0 mL, the injection temperature of the gold precursor solution may be 80 ° C-150 ° C, and the gold precursor solution. It was concluded that the reaction time after injecting the body solution could be 20-120 minutes.

Example III: characterization of hollow nanostructures

The surface morphology of the hollow nanostructures obtained in Example II was examined by a scanning electron microscope (SEM, Quanta FEG 650) manufactured by FEI equipped with an electric field emitter as an electron source. Transmission electron microscope (TEM) images were captured using a FEI Technai 20 microscope with an acceleration voltage of 200 kV. Energy dispersive X-ray spectrometer (EDS) mapping images and high angle annular dark field (HAADF) images were collected using ^{probe-corrected Titan 3} ™ 80-300S / TEM with an acceleration voltage of 300 kV. A UV-Vis-NIR spectrometer (Cary 5000) was used to record the extinction spectra of hollow nanostructures. To obtain an X-ray diffraction (XRD) pattern, a Bruker D8 Advance X-ray diffractometer with a CU Kα emission operated at a tube voltage of 40 kV and a current of 40 mA was used. The surface composition of Cu nanosheets was detected by using X-ray photoelectron spectroscopy (XPS, Kratos Axis). The device was disguised as a monochrome (Al Kα) X-ray gun. The binding energy was calculated by calibrating the binding energy of the C 1s peak to 284.6 eV.

2 to 7 show the structural and compositional properties of Cu-Au two-dimensional nanostructures prepared according to Example II (a).

From the scanning electron microscope (SEM) images of FIG. 2, it is clear that the hollow Au-Cu two-dimensional nanostructures have an average diameter of 75 nm. Since the galvanic substitution reaction does not change the size of Cu nanosheets based on the size range of 45 nm to several micrometers of the prepared Cu nanosheets, Cu-Au hollow two-dimensional nanostructures in the same size range can also be obtained. .. The galvanic substitution reaction was determined to affect the formation of cavities. Since the potential of ^{Au 3+ / Au (} 1.40V) is higher than that of ^{Cu 2+ / Cu (0.34V), this reaction, 2Au 3+} + 3Cu → 2Au + 3Cu ²⁺ , occurs naturally. Therefore, hollow nanostructures are formed by substitution of Cu atoms.

From the transmission electron microscope (TEM) image shown in FIG. 3 and the high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) measurement value shown in FIG. 5, it is further confirmed that the Cu-Au two-dimensional nanostructure has hollow pores. It is confirmed.

The high resolution TEM (HRTEM) images of the individual hollow nanostructures shown in FIG. 4 reveal that they contain large crystalline domains. Stripes with a lattice spacing of 2.225A can be indexed to the (111) plane of the face-centered cubic (fcc) alloy Cu-Au nanostructure.

FIG. 5 shows an energy dispersive X-ray (EDX) mapping image of hollow nanostructures. 6 and 7 show EDX mapping images of Cu element and Au element, respectively. As shown in FIGS. 5 to 7, both Cu and Au are uniformly distributed throughout the hollow nanostructure. This indicates that the Cu-Au hollow nanostructures are in the alloyed phase.

The transition of the pure Cu fcc phase to the alloy Cu-Au phase is further confirmed by X-ray diffraction techniques. FIG. 8 shows the Cu—Au alloy development process of Example II (a) over time. In particular, FIG. 8 shows a Cu—Au alloy development process in which the intensity of the Cu (111) diffraction peak decreases and the intensity of the Cu—Au (111) diffraction peak increases.

Specifically, FIG. 8 (a) shows that a pure Cu phase is obtained after injecting the Cu precursor at 300 ° C. over a reaction time of 60 minutes. The diffraction peak of Cu (111) is located at 43.7 ° as shown in FIG. 8 (a).

After injecting the Au precursor into the Cu nanosheet solution at 120 ° C. for a reaction time of 5 minutes, FIG. 8 (b) shows the formation of a mixed phase, which has a diffraction peak of Cu—Au (111) of 40.8. This is because it appears in °. As shown in the inserted SEM image 81 and TEM image 82, it is further confirmed from the porous structure that a galvanic substitution reaction occurs on the surface of the Cu sheet.

When the reaction time was extended to 20 minutes, FIG. 8 (c) shows that the diffraction peak of Cu (111) was reduced to almost negligible, which means that the product was Cu-Au at this point. It means that it is biased toward the alloy phase. Under the same feed concentration of Au precursor, the concentration of Cu was determined to decrease with reaction time. If the reaction time is less than 5 minutes, the molar ratio of Cu to Au is about 3: 1. When the reaction time is extended to 40 minutes, the molar ratio of Cu to Au decreases to 1: 3. The final molar ratio of Cu to Au reaches 1: 8 after extending the reaction time to 60 minutes. Since the reaction rate of galvanic substitution increases with the concentration of Au precursor, it was found that the molar ratio of Cu to Au and the time required to form a hollow structure decrease with increasing concentration of Au precursor. rice field. Therefore, the composition and phase of Cu-Au two-dimensional nanostructures can be adjusted by controlling the reaction time and the injection concentration of Au precursors.

The electronic properties and surface composition of the Cu-Au two-dimensional nanostructures were further investigated by X-ray photoelectron spectroscopy (XPS). 9A and 9B show well-resolved peaks from Au 4f and Cu 2p in the XPS spectrum. Both peaks of Cu 2p are positively shifted, that is, 0.2 eV for _{Cu 2p 1/2 and} 0.3 eV for _{Cu 2p 5/2.} The change in binding energy may be due to the electronic transition from Cu to Au, which is also explained by the work function difference of 4.65 eV for Cu (111) and 5.10 eV for Au (111). be able to. Furthermore, both peaks of Au 4f are also positively shifted, that is, _{0.2 eV for Au 4f 7/2 and} 0.13 eV for Au 4f _5/2 , respectively. This change is due to Au causing the surface ligand to lose electrons. XPS analysis showed the absence of isolated Au or Cu phases within the two-dimensional nanostructures, which is consistent with XRD results and EDX mapped images.

The phase transition from pure Cu to a Cu-Au alloy can also be visualized by the redshift of its scattering spectrum. The absorption peak of pure Cu nanosheets is located at about 600 nm. After forming the Cu-Au two-dimensional hollow nanostructure, the quenching peak is redshifted to the infrared region (center is 1500 nm) as shown in FIG. This red shift may be due to a decrease in aspect ratio during galvanic substitution or a change in electronic structure due to the phase transition. Cu-Au two-dimensional hollow nanostructures with unique optical properties have potential applications in the fields of surface-enhanced Raman scattering (SERS), sensing, and biomedicine.

11A and 11B show images of SEM111 and TEM112 hollow nanostructures of Cu-Pd and Cu-Pt prepared according to Examples II (b) and II (c), respectively. In particular, these SEM and TEM images are hollow Cu-Pd and Cu-Pt two-dimensional nanos due to the higher oxidation potentials of ^{Pd 2+} / Pd (0.92V) and Pt ^{2+ / Pt (1.20V).} Indicates that the structure is formed. The size of these two types of hollow nanostructures can be controlled from 50 nm to several micrometers.

FIG. 11C shows SEM111 and TEM112 of Cu-Au nanotubes prepared according to Example II (d). In particular, TEM images 111 show that Cu-Au nanotubes have rough surfaces and sharp tips, which can act as highly efficient catalysts for reducing _{CO 2 or for use as gas sensors.}

Claims (17)

The synthetic strategy comprises providing a first metal nanostructure having a plurality of first metal atoms and carrying out a synthetic strategy.
Replacing a part of the plurality of first metal atoms with a corresponding number of second metal ions,
And it promotes the diffusion of the first metal atom to provide a medium-air multi-metal nanostructure,
A method for preparing the hollow multimetal nanostructures comprising.
The hollow multi-metal nanostructure has at least one dimension of 0.1 to 100 nm, and the plurality of first metal atoms located away from the surface of the first metal nanostructure are the first metal. A portion of the plurality of first metal atoms at the surface and / or near the surface of the first metal nanostructure provided by the Kirkendall effect diffused to and / or near the surface of the nanostructure. Is a structure substituted with the corresponding number of the second metal ions.
The first metal atom has a first oxidation potential, the second metal ion is a metal ion having a second oxidation potential, and the second oxidation potential is the first oxidation potential. Higher than
The synthetic strategy heats a copper complex solution containing a plurality of copper complexes as the first metal atom at 100 to 500 ° C. to provide a copper nanostructured solution, and the copper nanostructured solution is subjected to the second. combined with a metal precursor solution containing a metal precursor containing the metal ions, the copper nano-structured solution and the metal precursor solution was combined, maintained at 100 ~ 500 ° C. over a synthesis time of 3 hours 1 minute A method of preparing a hollow multimetal nanostructure, including the above. The method according to claim 1, wherein the second oxidation potential is at least 0.6 V higher than the first oxidation potential. The method of claim 1, wherein the second metal is selected from the group consisting of gold, platinum, palladium, and combinations thereof. The metal precursors are _{from chloroauric acid (HAuCl 4} ), palladium (II) acetylacetonate (Pd (acac) ₂ ), chloroauric acid (H ₂ PtCl ₆ ), combinations thereof, and hydrates thereof. The method according to claim 1, which is selected from the group consisting of. The method according to claim 1, wherein the copper nanostructure solution is a copper nanosheet solution at 100 to 500 ° C., and the copper nanosheet solution is combined with the metal precursor solution. The keyed copper nanosheet solution and a metal precursor solution is maintained at the 100 ~ 500 ° C. over a synthesis time of 3 hours 1 minute A method according to claim 5. The method of claim 1, wherein the synthetic strategy is a one-step synthetic strategy. The one-step synthesis strategy, copper nanosheet solution containing the copper nano-sheet, comprising combining a metal precursor solution containing a metal precursor containing the second metal ions, the method of claim 7. The first metal atom has a first oxidation potential, the second metal ion is a metal ion having a second oxidation potential, and the second oxidation potential is the first oxidation potential. The method of claim 8 , which is higher than. The method according to claim 9 , wherein the second oxidation potential is at least 0.6 V higher than the first oxidation potential. The method of claim 9 , wherein the second metal is selected from the group consisting of gold, platinum, palladium, and combinations thereof. The metal precursors are _{from chloroauric acid (HAuCl 4} ), palladium (II) acetylacetonate (Pd (acac) ₂ ), chloroauric acid (H ₂ PtCl ₆ ), combinations thereof, and hydrates thereof. 8. The method of claim 8, selected from the group of The method of claim 8 , wherein the copper nanosheet solution is combined with the metal precursor solution at 50-180 ° C. The copper nanosheet solution and a metal precursor solution was combined is maintained at the 100 ~ 500 ° C. over a synthesis time of 3 hours 1 minute A method according to claim 13. Diffusion of copper atoms, a copper atom inside the copper nanostructures comprises diffusing to the outside of the copper nano-structure The method of claim 1. A hollow multi-metal two-dimensional nanostructure containing a plurality of first metal atoms and a plurality of second metal atoms.
The hollow multi-metal two-dimensional nanostructure has at least one dimension of 0.1 to 100 nm and is located on or near the surface of the first metal nanostructure having the plurality of first metals. It is a structure in which a part of the plurality of first metal atoms is replaced with a corresponding number of the plurality of second metal atoms.
The first metal nanostructure having the first metal atom is a first metal nanosheet containing the first metal atom.
The first metal is selected from the group consisting of copper, nickel, cobalt, iron, and combinations thereof.
The second metal is selected from the group consisting of gold, platinum, palladium, and combinations thereof.
Hollow multi-metal two-dimensional nanostructure. A method of preparing hollow multimetal nanostructures,
The plurality of first metal nanostructures at a position away from the surface of the first metal nanostructure having at least one dimension of 0.1 to 100 nm and having a plurality of first metal atoms. The plurality of metal atoms provided by the Kirkendall effect of diffusing metal atoms on and / or near the surface of the first metal nanostructure on the surface and / or near the surface of the first metal nanostructure. It is a structure in which a part of the first metal atom is replaced with a corresponding number of second metal ions.
A copper complex solution containing a plurality of copper complexes as the first metal atom is heated at 100 to 500 ° C. to prepare a copper nanostructured solution.
Preparing a metal precursor solution containing a second metal ion, wherein the second metal is different from the first metal and is oxidized at least 0.6 V higher than the oxidation potential of the first metal. Having potential, preparing and
Said copper nanostructure solution and combined the metal precursor solution, the copper nano-structured solution and the metal precursor solution was combined, maintained at 100 ~ 500 ° C. over a synthesis time of 3 hours 1 minute, the copper To form a hollow nanostructure containing the copper and the second metal by substituting the plurality of copper atoms on the surface and / or near the surface of the nanostructure with the second metal ion.
Including methods.

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